The present invention relates to an air bag to protect a person in vehicle by inflating with reaction gas from an inflator when the vehicle is collided, and in particular to an air bag provided with a suspension string to maintain the shape of the air bag to the predetermined shape when it is inflated.
The air bag unit installed on a fixed portion of car body in front of the seat in a vehicle plays an important role in protecting persons in the vehicle from injury when they are collided against car body as the air bag is instantaneously inflated by the pressure of reaction gas released from an inflator fixed on steering wheel or dashboard during an emergency such as the collision of the vehicle.
For example, as shown in FIG. 4, the air bag unit comprises an inflator 2, which ejects reaction gas by bringing a gas generating agent to chemical in response to a collision signal from a collision detecting sensor when the deceleration of the vehicle exceeds a certain level, and an air bag 3, which is inflated by the gas ejected from the inflator 2 and the base of which is fixed to the inflator 2. This air bag unit is mounted on a fixed portion of car body, such as the center of the steering wheel 5, by folding the air bag 3 and placing it into a pad 4.
As shown in FIG. 5, the gas generating agent in the inflator 2 is brought into reaction when the vehicle collides, and the air bag 3 is instantaneously inflated by the generated reaction gas. Thus, the air bag 3 receives the person M, who is moved forward by inertia and protects the person M from the collision against the car body. In this case, in order that the air bag does not unnecessarily protrude toward the person M, the shape of the inflated air bag 3 is maintained in the predetermined shape by a suspension member 6 furnished between the base cloth 3a on the side facing to the person M and the base cloth 3b on the fixed portion of car body or between the base cloth 3a and the fixed portion of car body. Thus, it is possible to effectively receive the person M.
As the methods for fixing the suspension member 6 on base cloth 3a on the side facing to the person M, the following three methods have been adopted in the past:
FIG. 6 shows one of such methods. In the Figure, the same components as in FIG. 5 are referred by the same numbers and symbols, and detailed description is not given here.
As shown in FIG. 6, two pieces of catch cloths 7 and 8 are fixed on the base cloth 3a on the side facing to the person M by the sewn portion a in approximately circular shape, and one end of each of 4 single straps 6a, 6a, . . . , consituting the suspension member 6, is fixed on 4 suspension member attachments 7a, . . . , 8a, . . . , of these catch cloths 7 and 8 by the sewn portion b. This method is advantageous in that the strength of the suspension member 6a at the sewn portion b is relatively high.
FIG. 7 shows another of the above methods. The same component as in FIG. 5 are referred by the same member and symbol, and detailed description is not given here.
As shown in FIG. 7, the suspension member 6 consists of a sewn portion 6b at the center of the cloth and 4 connecting legs 6c, 6c, . . . , extending in form of a cross in the 4 directions from the sewn portion 6b, and the sewn portion 6b of the suspension member 6 is fixed by the sewn portion a on the base cloth 3a. This method is advantageous in that the manufacturing process is simplified and the air bag can be designed in a lightweight and compact form because fewer components are used.
FIG. 8 shows the last of the above three methods. The same component as in FIG. 5 are referred by the same numbers and symbols, and detailed description is not given here.
As shown in FIG. 8, the suspension member 6 consists of a pair of single straps 6.sub.1 and 6.sub.2 of identical shape. This single strap 6.sub.1 and 6.sub.2 are formed by two connecting legs 6e and 6e, which integrally extend toward 2 directions, perpendicular to each other, from the sewn portion 6d. With these connecting legs 6e and 6e making a cross and with the sewn portions 6d and 6d partially overlapped on each other in A, these sewn portions 6d and 6d are fixed on the base cloth 3a by the sewn portion a in circular shape. This method is advantageous that the base cloth can be effectively cut and that the manufacturing process is simplified and the air bag can be designed in a lightweight and compact form because fewer components are used.
However, these methods have the following problems:
In the method of FIG. 6, many components are used and this results in a complicated manufacturing process and high cost. Also, the air bag is heavier in eight, difficult to fold up, and requires a larger space to store.
In the method of FIG. 7, the base cloth cannot be cut effectively and this means higher cost. Also, the strength of the sewn portion of the suspension member 6 is weaker than in the method of FIG. 6.
In the method of FIG. 8, the sewn portions 6d and 6d of a pair of single straps 6.sub.1 and 6.sub.2 are partially overlapped with each other, whereas the strength of the sewn portion of the suspension string 6 is weak because the sewn portion a on the overlapping A is small. Also, because the sewn portions 6d and 6d are partially overlapped on each other, the positioning of single straps 6.sub.1 and 6.sub.2 is difficult.
To solve the above problems, it is an object of the present invention to offer an air bag, by which the base cloth of the suspension member can be effectively cut and the strength of the sewn portion suspension member can be made stronger.
Another object of the invention is to offer an air bag, which is lightweight and compact, and which can be manufactured by a simplified manufacturing process because few components are used.